Cardiovascular diseases are the leading cause of death in the world. Cardiac transplantation, which is currently the sole therapeutic option for severe heart failure patients, suffers from donor shortage. A potential alternative therapeutic option to the cardiac transplantation is transplantation of cardiomyocytes derived from pluripotent stem cells such as iPS and ES cells. Practical use of the alternative therapy is highly desired. However, before practically using cardiomyocytes derived from pluripotent stem cells in tissue engineering, problems of safety and preparation cost must be resolved.
For the transplantation of cardiomyocytes to a human, it is estimated that at least as much as 109 cells are necessary. However, currently available methods for inducing cardiac differentiation of pluripotent stem cells require proteins such as growth factors, cytokines and serum albumin in vast amounts, and are highly expensive. More specifically, for preparing 109 cardiomyocytes, at least ten liters of culture media are necessary, which would cost more than ten million yen. Actually, currently commercially available cardiomyocytes derived from human pluripotent stem cells are as expensive as several hundred thousand yen per 106 cells, which corresponds to that the 109 cells required for a single transplantation procedure cost several hundred million yen. Therefore, if the cost of the culture media necessary for inducing the cardiac differentiation is reduced, the cardiac tissue engineering will become more practical.
The culture media currently used in the induction of cardiac differentiation of pluripotent stem cells comprise cytokines or proteins and is potentially accompanied by safety problems. In particular, the proteins are obtained from animal cells, bacteria or yeast, and are potentially contaminated with viruses, mycoplasmas, prions or the like from the host cells. However, such contamination must be eliminated from the step of inducing cardiac differentiation of pluripotent stem cells, because the cardiomyocytes from this step are directly provided for the transplantation into a patient.